JP4432077B2 - Mouth tube section of synthetic resin housing - Google Patents

Description

  The present invention relates to a structure of a mouth tube portion of a synthetic resin casing made by stretch blow molding with a polyethylene terephthalate resin or the like.

  Patent Document 1 describes a biaxially stretched blow molded casing made of polyethylene terephthalate resin (hereinafter referred to as a PET bottle) used for products having a high temperature filling or heat treatment process such as tea and fruit juice beverages. However, PET bottles for products with high temperature (about 80-90 ° C.) or heat treatment processes such as tea, fruit juice drinks, liquid seasonings, etc. are so-called heat distortion strength enhanced by thermal crystallization treatment. A heat-resistant mouth tube is used.

FIG. 8 shows a typical example of the heat-resistant mouthpiece portion shown in Patent Document 1, but the whole mouthpiece portion is whitened by the thermal crystallization treatment, and the screw thread 3 is opened at the bottom of the screw thread 3 by an unauthorized operation or an erroneous operation. A neck ring 9 is provided together with a bead ring 8 for a pilfer-proof screw cap having a function of preventing the above. Here, hatching by the mesh in FIG. 8 represents a whitening state by thermal crystallization.
Japanese Patent Laid-Open No. 10-058527

  In recent years, the PET bottle is also used for retort foods that require high-temperature sterilization at about 130 ° C.

  Here, heat shrinkage deformation occurs due to the thermal crystallization treatment of the mouth tube portion. For example, from the viewpoint of resource saving, the wall thickness of the tube wall 2 or the dimensions of the bead ring 8, particularly the height and width are greatly increased. In order to obtain heat resistance that can be used as a retort food container, a heat crystallization process at a high temperature of about 180 ° C. is necessary. There is a problem in that the upper end surface of the cylindrical wall 2 is improperly contracted, which impairs the sealing performance when screwed.

  The cause of incorrect shrinkage is mainly related to the difference in the circumferential direction of the thread shape formed on the outer peripheral surface of the cylinder wall (for example, the start end of the thread), and this difference causes resin flow and cooling solidification during injection molding. It is considered that the behavior is affected and illegal closing occurs. For example, if the wall thickness of the cylinder wall is reduced, the difference in the shape of the thread in the circumferential direction is emphasized, so that the shrinkage becomes larger. If the high temperature of the thermal crystallization treatment is set to a high temperature of about 180 ° C., the heat shrinkage is increased. The non-uniformity is further increased.

  Therefore, the present invention was devised to solve the above-described problems in the prior art, and the influence of the thread forming portion on the flow and the cooling and solidification behavior of the molten resin can be made along the circumferential direction of the mouth tube portion. It is a technical problem to make them uniform as much as possible, and it aims at having high pressure resistance and heat resistance, and stably obtaining high sealing performance and resource saving.

The means of the invention according to claim 1 for solving the technical problem is as follows:
In the mouthpiece portion of the synthetic resin casing formed by biaxial stretch blow molding of the injection-molded preform,
Forming a concave groove along the circumferential direction for suppressing the occurrence of shrinkage due to thermal crystallization treatment on the upper end surface of the cylindrical wall at the height position above the screw thread on the outer peripheral surface of the cylindrical wall of the mouth tube portion; And whitening by thermal crystallization treatment.

  The reason for the occurrence of shrinkage (concave portion) due to thermal crystallization on the upper end surface of the conventional mouth tube portion is estimated as follows. That is, in biaxial stretch blow molding, a test tubular preform by injection molding is used, and in this injection molding, the molten resin is injected from the bottom of the preform and flows toward the upper end surface of the mouth tube portion. Depending on the shape of the screw thread on the tube wall, such as the position of the portion or the terminal end, the number of overlapping threads, and the like, the flow state of the resin can vary greatly in the circumferential direction of the mouth tube.

  In addition, since the vicinity of the upper end surface of the cylindrical wall is near the end of the flow, the resin temperature is low, and due to the influence of the flow state, the difference in pressure state and the difference in molecular orientation increase, and this is the final stage of flow. Immediately after the mold clamping and cooling process, the time for relaxing the molecular orientation is short, and the difference in the molecular orientation state generated during the flow remains in the molded product. This is considered to be because a large difference in shrinkage occurs in the crystallization behavior.

  More specifically, when there are a thin part and a thick part in the circumferential direction of the mouth tube part, the degree of molecular orientation in the thin part increases due to resin flow, and the degree of molecular orientation in the cooled and solidified state is It becomes relatively large. On the other hand, the progress of crystallization due to thermal crystallization in a portion with a large molecular orientation is relatively slow, and the increase in density is relatively small. As a result, the amount of shrinkage due to thermal crystallization is relatively small in the thin-walled portion, and conversely, the shrinkage is relatively large in the thick-walled portion, and there is a difference in the amount of shrinkage as seen in the circumferential direction, resulting in shrinkage.

  And the main element of the thin part and the thick part in the circumferential direction of the mouth tube part here is the arrangement shape of the screw thread, for example, it becomes relatively thin at the start end part or the end part vicinity of the screw thread. A portion formed by overlapping a plurality of mountains is a thick portion.

  In addition, even when heat treatment at a relatively low temperature is in an allowable range from the viewpoint of sealability and the like, if the heat treatment temperature is increased to about 180 ° C. in order to further improve heat resistance, the amount of heat shrinkage It is sufficiently estimated that the non-uniformity of the shrinkage amount becomes large as the value of becomes large.

  Here, for example, when the thickness of the mouth tube portion is sufficiently increased, the ratio of the resin flow path between the portion with and without the thread is reduced, and the difference in molecular orientation state generated during flow is reduced. However, it is difficult to sufficiently reduce the difference in the molecular orientation state within the practical thickness range from the viewpoint of productivity, cost reduction, resource saving, and the like of the PET bottle.

The configuration according to claim 1 is created based on the above-described idea,
A concave groove is formed along the circumferential direction over a predetermined center angle position and a predetermined center angle range above the upper end portion of the outer peripheral surface of the cylindrical wall, above the screw threads, and particularly in consideration of the arrangement of the threads. By narrowing the flow path of the resin accordingly at the circumferential position where the concave groove is formed, the flow state of the resin as a whole is adjusted to reduce the difference between the flow state in the circumferential direction and the molecular orientation state. It is possible to effectively suppress the occurrence of shrinkage at the upper end surface of the mouth tube portion due to the thermal crystallization process.

  Here, the effect of forming the concave groove can be exhibited even when the formation depth is, for example, about 1/10 of the wall thickness of the cylindrical wall. In the range that does not impair the sealing performance formed by the outer peripheral surface directly below the end surface and the upper end portion of the inner peripheral surface of the screw cap, it is possible to suppress the occurrence of shrinkage and to make the appearance inconspicuous. It becomes possible.

  The above-described operation effect of the concave groove is considered to be because the concave groove is formed in the vicinity of the end of the resin flow above the screw thread. In other words, in the very vicinity of the flow end, the resin temperature is considerably lowered and the resin viscosity is high, so that the molecular orientation state can be sufficiently adjusted by slightly changing the flow path depth.

  In addition, various grooves can be formed by changing the number of grooves, formation height position, circumferential position and formation range, groove depth, groove width, etc. Can experimentally confirm the degree of shrinkage and determine the optimal groove formation mode.

  According to a second aspect of the present invention, in the first aspect of the invention, the concave groove is formed in a circumferential groove shape.

  According to the above configuration of the second aspect, the concave groove can be formed in the simplest shape. Further, even if the concave grooves having the same cross-sectional shape are formed in a circumferential groove shape, it is possible to suppress non-uniformity of resin flow in the circumferential direction. That is, it is possible to impart a flow history exceeding the difference in the circumferential direction of the resin flow history that has passed through the thread portion to the molten resin by the concave groove formed in the circumferential groove shape, and to make the flow state more uniform. .

  Further, by forming the concave groove by changing the depth or the like in the circumferential direction depending on the state of occurrence of the shrinkage, the occurrence of the shrinkage can be more effectively suppressed.

  According to a third aspect of the present invention, in the first aspect of the invention, the concave groove is intermittently formed into a circumferential groove shape.

According to the configuration of claim 3, the flow state in the circumferential direction can be adjusted with a simple shape by forming the concave groove intermittently in a circumferential groove shape while observing the state of occurrence of shrinkage, which is effective. The occurrence of shrinkage can be suppressed.
In addition, the structure of this claim shall include the case where one location of the circumferential groove-shaped concave groove is missing.

  According to a fourth aspect of the present invention, in the third aspect of the invention, there is provided a concave groove not forming a concave groove in a range extending from 10 ° to 50 ° in the central angle with respect to the position near the starting end of the main body of the screw thread. To be a part.

  At the starting end of the thread main body, the flow path changes rapidly in the circumferential direction by the height of the thread thread. Although the detailed mechanism is not always clear at present, there is a case where the closeness estimated to be caused by the main body start end position frequently occurs at a position of a certain center angle from the main body start end.

  Therefore, according to the above-described configuration of the fourth aspect, the concave groove is formed by setting the range extending from 10 ° to 50 ° around the position near the starting end of the main body of the screw thread as the concave groove not portion that does not form the concave groove. By narrowing the resin flow width in the region, it is possible to adjust the influence of a sudden change in the flow state of the resin in the vicinity of the starting end of the screw thread during injection molding of the preform, and the position of a constant central angle from the starting end of the main body In particular, it is possible to effectively suppress shrinkage that occurs frequently.

  According to a fifth aspect of the present invention, in the first, second, third, or fourth aspect of the invention, the start end extension is obtained by gently reducing the width and height of the thread from the start end and the end of the main body of the thread, respectively. The extension part and the terminal extension part.

  6. The resin flow in the vicinity of the main body start end and main body end of the screw thread during the injection molding of the parison by the start end extension and the end extension by gently reducing the width and height of the screw thread. A sudden change in the state can be avoided, and the occurrence of shrinkage at the upper end surface of the mouth tube portion can be more effectively suppressed in combination with the action of the groove.

  According to a sixth aspect of the present invention, in the first, second, third, fourth, or fifth aspect of the present invention, a plurality of threads are formed in the mouth tube portion in a multi-threaded shape.

  In the case for retort foods, the content liquid is often in the form of a paste, and a wide-mouthed bowl is used in consideration of taking it out with a spoon, etc., but while reducing the amount of rotation operation required for attaching and detaching the screw cap, The multi-threaded screw structure is adopted with little exception so that the amount of the synthetic resin material required for molding the mouth tube portion is reduced and the height of the mouth tube portion of the housing is not excessive.

  Here, according to the above-described configuration of the sixth aspect, in the case where the thread is a multi-threaded thread, the cause of occurrence of shrinkage such as the presence of a plurality of main body start ends or main body end points becomes complicated. By observing, it is possible to effectively suppress the occurrence of shrinkage even in the high-temperature heat treatment for retort food by forming the concave groove at a predetermined position in relation to the state of occurrence of the shrinkage.

  According to a seventh aspect of the present invention, there is provided the invention according to the first, second, third, fourth, fifth or sixth aspect, wherein the mouth tube portion has a structure in which a bead ring and a neck ring are provided below the screw thread. And the neck portion including the neck ring is whitened by thermal crystallization.

  According to the above-described configuration of the seventh aspect, a bead ring and a neck ring are attached to the mouth tube portion below the thread as necessary, and the mouth tube portion including the bead ring and the neck ring is whitened by thermal crystallization. However, since the bead ring and the neck ring form a relatively thick portion around the entire circumference of the lower portion of the mouth tube portion, the influence of the thread on the resin flow can be alleviated to some extent.

The present invention has the above-described configuration, and has the following effects.
In the first aspect of the present invention, the resin flow state is adjusted by forming the concave groove along the circumferential direction over a predetermined position and center angle range, and the flow state and molecular orientation state in the circumferential direction are adjusted. Difference can be reduced, and the occurrence of shrinkage at the upper end surface of the mouth tube portion due to the thermal crystallization treatment can be effectively suppressed.

  Since the concave groove is formed very close to the end of the resin flow, the effect of forming the concave groove is exhibited even when the formation depth is, for example, about 1/10 of the wall thickness of the cylinder wall.

  In the invention according to the second aspect, the concave groove can be formed in the simplest shape by forming the peripheral groove shape. Further, it is possible to make the flow state uniform by adding a flow history exceeding the difference in the circumferential direction of the resin flow history that has passed through the thread portion to the resin through the concave groove.

  In the invention of claim 3, the flow state in the circumferential direction can be effectively adjusted with a simple shape by intermittently forming the concave groove into a circumferential groove shape while observing the state of occurrence of shrinkage. Can do.

  In the invention according to claim 4, the influence of the rapid change in the flow state of the resin in the vicinity of the main body start end of the screw thread can be adjusted, and it occurs frequently at a position of a constant center angle from the main body start end. Close can be effectively suppressed.

In the invention of claim 5, it is possible to avoid a sudden change in the flow state of the resin in the vicinity of the main body start end and the main body end of the screw thread during the injection molding of the parison by the start end extension and the end extension. Combined with the action of the concave groove, it is possible to more effectively suppress the occurrence of shrinkage at the upper end surface of the mouth tube portion.

  In the invention according to claim 6, even if the mouth tube portion having a multi-threaded screw thread having a complicated cause of the shrinkage is observed, the occurrence state of the shrinkage is observed. By forming the concave groove at a predetermined position while being related to the above, it is possible to effectively suppress the occurrence of shrinkage, and it can be widely used for retort foods.

  In the invention described in claim 7, since the influence of the thread on the resin flow can be alleviated to some extent by bead ring or the like, the occurrence of shrinkage can be more effectively suppressed.

Embodiments of the present invention will be described below with reference to the drawings.
1 to 5 show one embodiment of the mouthpiece portion 1 of the present invention, and FIG. 1 shows an overall front view of a casing having one embodiment of the mouthpiece portion 1 of the present invention. The casing is a biaxially stretched blow-molded product made of PET, and the upper end of the barrel portion 12 having a bottomed cylindrical shape is connected to the mouth tube portion according to the present invention via a shoulder portion 11 having a truncated pyramid shape. 1 is constructed by standing upright. In addition, although the mesh-shaped hatching of FIG. 1 represents the whitening state by a thermal crystallization process, in order to show a shape clearly in FIGS. 2-4, this hatching is abbreviate | omitted.

  The mouth tube portion 1 has a multi-thread structure in which three threads 3 having a continuous thread structure are provided in the upper half of the outer peripheral surface of a cylindrical wall 2 having a cylindrical shape. Is provided with a bead ring 8 that is not continuous with the screw thread 3 and has a small height and is exclusively used for a synthetic resin pilfer-proof screw cap. A neck ring 9 that functions as a ring is provided.

  The entire mouthpiece portion 1 including the neck ring 9 is whitened by thermal crystallization. However, this thermal crystallization process is not limited to the mouthpiece portion 1 alone. The upper end of the neck, which is a connecting portion between the shoulder 11 and the shoulder 11 may be thermally crystallized together. In some cases, the entire region of the neck may be thermally crystallized with a low degree of crystallization.

  Each screw thread 3 (3a, 3b, 3c) reduces the height and width of the screw from the main body start end 3s (3sa, 3sb, 3sc) and main body end 3e (3ea, 3eb, 3ec) toward the tip. The start end portion 4 (4a, 4b, 4c) and the end portion 5 (5a, 5b, 5c) are formed, and each screw thread 3 is formed over a central angle of 237 ° including the start end portion 4 and the end portion 5. 3 threads 3 are arranged at an equal central angle. In the following description, when referring to individual threads among the three threads, a, b, and c are added to the reference numerals.

  In addition, circumferential grooves 6 are intermittently formed at positions directly above the upper end of the thread 3 except for the recessed groove notches 7 arranged at three locations (see FIGS. 4 and 5). In this embodiment, the groove depth of the concave groove 6 is about 1/10 of the cylindrical wall 2, and the range of the concave groove notch 7 is 40 ° in the central angle.

  Here, the arrangement position of the recessed groove notch portion 7 is determined by observing the occurrence position of the shrinkage in the mouth tube portion 1 where the recessed groove 6 is not formed, and associating the generated position with the arrangement form of the screw thread 3 and the like. Along with the experiment, it can be determined in consideration of the flow state of the resin. FIG. 6 shows a comparative example of the mouth tube portion 1 similar to the present embodiment except that the concave groove 6 is not formed, and a part of the mouth tube portion 1 is similar to FIG. 5 of the present embodiment. It is explanatory drawing which expands and shows.

  When the mouthpiece part 1 of the comparative example shown in FIG. 6 was subjected to thermal crystallization treatment at 180 ° C., significant shrinkage was observed at three positions h1, h2, and h3 shown in FIG. Further, the position where this shrinkage occurs is from 20 to 40 ° in the center angle in the screwing direction from the main body starting ends 3sa, 3sb and 3sc of the screw threads 3a, 3b and 3c (from the position indicated by the dashed line in FIG. 6). It was a position.

  In this embodiment, the shrinkage occurs remarkably at a high frequency in the range of 20 to 40 ° in the screwing direction from the main body start end 3s of each screw thread 3 as in the generation positions h1, h2, and h3. In addition, the main body end 3e may be located adjacent to the main body start end 3s, so that the resin flow path is narrowed as a whole, and the central angle around the vicinity of the main body start end 3s is 40 °. The extending range is defined as a concave groove notch 7 and the concave groove 6 is intermittently formed in a circumferential groove shape.

  That is, in the vicinity of the end of the resin flow, the resin flow in the portion other than the concave groove notch 7 is narrowed by the concave groove 6 so as to adjust the entire resin flow. Due to the formation of the concave groove 6, the occurrence of shrinkage at each of the occurrence positions h1, h2, and h3 was suppressed, and the sealability and external appearance of the screw cap could be allowed.

  The resin flow in the vicinity of the upper end of the mouth tube during injection molding of the preform is complicated, and a mechanism in which the main body start ends 3sa, 3sb, 3sc are dragged at a center angle of 20 ° to 40 ° in the screwing direction. Is not necessarily clear, but at least by changing the formation mode of the groove 6 while associating the position of occurrence of shrinkage and the shape of the thread 3 as in this embodiment, the thickness of the cylindrical wall 2 as in this embodiment is changed. It was found that the flow behavior or crystallization behavior of the resin at both flow ends can be adjusted even by the concave groove 6 having a thickness of about 1/10.

  That is, first, a portion where the shrinkage occurs in a state where the concave groove 6 is not formed is specified, and the relationship between the generation position and the shape of the screw thread 3 is observed, and the concave portion is formed at a predetermined position according to the relationship. By forming the groove 6, the flow state or the crystallization behavior can be adjusted, the shrinkage accompanying the crystallization can be made uniform in the circumferential direction, and the occurrence of shrinkage can be effectively suppressed.

  FIG. 7 shows another embodiment of the mouth tube portion 1 of the present invention, and is an explanatory view showing a part of the mouth tube portion 1 in an expanded manner as in FIG. In the embodiment shown in FIGS. 1 to 5, a start end extension 4p (4pa, 4pb) in which the start end 4 and the end end 5 of the screw thread 3 are further lengthened and the width and height of the screw thread 3 are gradually reduced. 4pc) and the terminal extension 5p (5pa, 5pb, 5pc) are extended, and other configurations such as the formation of the groove 6 are the same as those in the above-described embodiment.

  The resin flow state in the vicinity of the main body start end 3s and the main body end end 3e of the screw thread 3 at the time of parison injection molding by the start end extension 4p and the end extension 5p with the width and height of the screw thread 3 gradually reduced. Therefore, the occurrence of shrinkage at the upper end surface of the mouth tube portion 1 can be further suppressed in combination with the action of the concave groove 6.

  In the above two embodiments, the example in which one thread is taken out of the three threads formed by the concave groove and the shrinkage thereof is suppressed has been described. The effect of the suppression is generally exhibited in the mouth tube portion used by thermal crystallization treatment. Needless to say, for example, even in the case of a single screw or a double screw, a screw thread start end, Suppression of shrinkage caused by non-uniform resin flow caused by the thread end portion or the like can be effectively suppressed.

  Moreover, not only in the heat crystallization process at a high temperature of 180 ° C. for retort foods, for example, in the mouth tube part in which a notch is formed in a screw thread for degassing, a remarkable shrinkage occurs even at a relatively low temperature. Even in such a case, the effect of the formation of the concave groove of the present invention is expected, and the present invention can be applied to various screw thread forms.

  In addition, not only the formation position of the groove, but also the depth, width, etc. of the groove as long as the groove does not impair the sealing performance with the screw cap at the upper end of the outer peripheral surface of the cylindrical wall. It is also possible to change the flow rate, or to arrange a plurality of circumferential grooves, and the like can be used as means for adjusting the flow state.

  As described above, the mouthpiece portion of the present invention effectively suppresses the occurrence of shrinkage at the upper end surface even in the thermal crystallization process for retort food by forming a concave groove at the upper end portion of the outer peripheral surface of the mouthpiece portion. It can be used for various screw thread shapes and is expected to be used in a wide range of applications.

It is a front view of the synthetic resin casing which has one Example of the mouth tube part of this invention. It is a front view which shows the mouth tube part of FIG. It is a longitudinal cross-sectional view of the mouth tube part of FIG. It is a top view of the mouth tube part of FIG. It is explanatory drawing which expands and shows a part of mouth tube part of FIG. It is explanatory drawing which expands and shows a part of mouth tube part of a comparative example. It is explanatory drawing which expands and shows a part of mouth tube part other Examples of this invention. It is a front view which shows the conventional heat-resistant mouth tube part.

Explanation of symbols

1; mouth tube portion 2; tube wall 2f; upper end surface 3 (3a, 3b, 3c); thread 3s (3sa, 3sb, 3sc); main body start end 3e (3ea, 3eb, 3ec); main body end 4 (4a, 4b, 4c); start end 5 (5a, 5b, 5c); end 4p (4pa, 4pb, 4pc); start end extension 5p (5pa, 5pb, 5pc); end extension 6; concave groove 7; concave groove Notch 8; bead ring 9; neck ring 11; shoulder 12; trunk h 1, h 2, h 3;

Claims (7)

It is a mouth tube part of a synthetic resin casing formed by biaxial stretching blow molding of an injection-molded preform, and a cylindrical wall (2) on the outer peripheral surface of the cylindrical wall (2) at a height position above the thread (3). In the upper end surface (2f) of 2), a concave groove (6) for suppressing the occurrence of shrinkage due to thermal crystallization treatment is formed along the circumferential direction, and the synthetic resin casing whitened by thermal crystallization treatment is formed. Muzzle part.
The mouth tube portion of the synthetic resin casing according to claim 1, wherein the concave groove (6) is formed in a circumferential groove shape. The mouth tube portion of the synthetic resin casing according to claim 1, wherein the concave groove (6) is intermittently formed in a circumferential groove shape. 4. A concave groove notch (7) that does not form a concave groove (7) is defined in a range from 10 ° to 50 ° as a central angle centered on the vicinity of the main body start end (3s) of the screw thread (3). A mouth tube portion of the described synthetic resin casing. Request for extending the end extension (4p) and the end extension (5p) by gradually reducing the width and height of the thread from the main end (3s) and main end (3e) of the thread (3). Item 5. A cylindrical portion of the synthetic resin casing according to item 1, 2, 3 or 4. The mouth tube part of the synthetic resin casing according to claim 1, 2, 3, 4, or 5 having a plurality of screw threads (3) in a multi-threaded shape. A structure in which a bead ring (8) and a neck ring (9) are attached below the thread (3), and the bead ring (8) and the neck ring (9) are included, and the claim is whitened by thermal crystallization treatment. Item 1. A cylindrical portion of the synthetic resin casing according to item 1, 2, 3, 4, 5 or 6.

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